The Kohler LH640 is a 624 cc (38.1 cu·in) natural aspirated V-twin four-stroke liquid-cooled internal combustion small gasoline engine with a horizontal shaft from the Aegis series, manufactured by Kohler Co for general-purpose applications.
It has an 77.0 mm (3.03 in) cylinder bore and 67.0 mm (2.64 in) piston stroke. The compression ratio rating is 8.5:1.
This engine produced 24.3 PS (17.9 KW; 24.0 HP) at 3,600 rpm of maximum horsepower and 51.9 Nm (5.29 kg·m; 38.3 ft·lb) at 2,400 rpm of peak torque.
The Kohler Aegis LH640 features:
- OHV (overhead valve) design
- Hydraulic valve system
- Electronic ignition system
- One-barrel carburetor with fixed main jet (Keihin)
- Centrifugal flyweight mechanical governor
- Full pressure with Gerotor oil pump lubrication system
- Liquid-cooled cooling system with parallel-flow radiator and integrated belt-driven water pump
- Solenoid shift starter (12V)
General information
Engine Specifications | |
Engine model | Aegis LH640 |
Engine type | 4-stroke, OHV, V-twin |
Displacement | 624 cm3, (38.1 cu·in) |
Max. horsepower | 24.3 PS (17.9 KW; 24.0 HP) at 3,600 rpm |
Max. torque | 51.9 Nm (5.29 kg·m; 38.3 ft·lb) at 2,400 rpm |
Cooling system | Liquid-cooled |
Air cleaner | Heavy-Duty air cleaner |
Lubricating system | Full pressure with gerotor oil pump |
Ignition system | Electronic ignition system |
Fuel system | Carburetor with fixed main jet (Keihin) |
Fuel used | Unleaded gasoline (octane number 86 or higher) |
Starting system | Solenoid shift starter (12V) |
Charging system | 20A charging, regulated |
Governor | Centrifugal flyweight mechanical governor |
PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Dimensions (L x W X H) | 432 x 459 x 674 mm (17.0 x 18.1 x 26.5 in) |
Dry weight | 51.7 kg (114.0 lbs) |
Cylinder Block and Head
Cylinder block | |
Compression ratio: | 8.5:1 |
Cylinder bore: | 77.0 mm (3.03 in) |
Piston stroke: | 67.0 mm (2.64 in) |
Cylinder internal diameter (standard): | 77.000-77.025 mm (3.0315-3.0325 in) |
Piston skirt outer diameter (standard): | 76.968-76.986 mm (3.0302-3.0309 in) |
Number of piston rings (compression / oil): | 2/1 |
Connecting rod small end diameter (standard): | 17.015-17.023 mm (0.6699-0.6702 in) |
Piston pin diameter: | 16.995-17.000 mm (0.6691-0.6693 in) |
Side clearance (Top): | 0.040-0.086 mm (0.0016-0.0034 in) |
Side clearance (Second): | 0.040-0.086 mm (0.0016-0.0034 in) |
Side clearance (Oil): | 0.046-0.196 mm (0.0018-0.0077 in) |
Ring end gap (Top): | 0.180-0.380 mm (0.0071-0.0150 in) |
Ring end gap (Second): | 0.250-0.450 mm (0.0098-0.0177 in) |
Crankshaft main journal diameter: | 40.913-40.935 mm (1.6107-1.6116 in) |
Crankpin journal diameter: | 35.955-35.973 mm (1.4155-1.4163 in) |
Crankshaft center distance: | 33.5 mm (1.32 in) |
Cylinder head | |
Valve arrangement: | OHV, gear driven |
Valves: | 2 (4 valves in total) |
Valve head diameter (INTAKE): | 33.370-33.630 mm (1.3138-1.324 in) |
Valve head diameter (EXHAUST): | 29.370-29.630 mm (1.1563-1.1665 in) |
Valve face angle (INTAKE): | 45° |
Valve face angle (EXHAUST): | 45° |
Seat angle (INTAKE): | 89° |
Seat angle (EXHAUST): | 89° |
Valve steam diameter (INTAKE): | 6.982-7.000 mm (0.2749-0.2756 in) |
Valve steam diameter (EXHAUST): | 6.970-6.988 mm (0.2744-0.2751 in) |
Valve lift (min) (INTAKE): | 8.88 mm (0.3496 in) |
Valve lift (min) (EXHAUST): | 8.88 mm (0.3496 in) |
Camshaft journal diameter : | 19.962-19.975 mm (0.7859-0.7864 in) |
Tightening torque specs
Tightening torque specs | |
Intake manifold (torque in 2 increments) | Step 1: 7.4 Nm (0.8 kgf·m; 5.5 lb·ft) Step 2: 9.9 Nm (1.0 kgf·m; 7.3 lb·ft) |
Carburetor mounting | 9.9 Nm (1.0 kgf·m; 7.3 lb·ft) |
Connecting rod cap | 11.3 Nm (1.15 kg·m; 8.3 ft·lb) |
Oil drain plugs | 13.6 Nm (1.4 kg·m; 10.0 ft·lb) |
Cylinder head (torque in 2 increments) | Step 1: 16.9 Nm (1.7 kg·m; 12.5 ft·lb) Step 2: 33.9 Nm (3.5 kg·m; 25.0 ft·lb) |
Rocker pivot | 11.3 Nm (1.1 kg·m; 8.34 ft·lb) |
Rear fan shaft to mounting bracket nut | 15.8 Nm (1.6 kgf·m; 11.7 lb·ft) |
Front fan assembly to fan shaft nut | 15.8 Nm (1.6 kgf·m; 11.7 lb·ft) |
Flywheel | 66.4 Nm (6.77 kg·m; 49 ft·lb) |
Spark plug | 27 Nm (2.75 kg·m; 19.93 ft·lb) |
Muffler retaining nuts | 24.4 Nm (2.5 kg·m; 18.0 ft·lb) |
Valve cover | 6.2 Nm (0.63 kg·m; 4.6 ft·lb) |
Governor lever nut | 6.8 Nm (0.7 kgf·m; 5.0 lb·ft) |
Service Data
Engine | |
Idle speed: | 1200±75 rpm |
Compression pressure | |
Compression differential limit between cylinders: | 15% and less |
Oil system | |
Lubrication system: | Full pressure with gerotor oil pump |
Oil type: | SAE 10W-30 |
Recommended oil: | API SG, SH, SJ, or higher |
Oil capacity: | W/o oil filter: 1.6 liters (1.7 US.qts, 1.4 Imp. qts) With oil filter: 1.8 liters (1.9 US.qts, 1.58 Imp. qts) |
Ignition system | |
Type: | Electronic ignition system |
Spark plug: | Champion RC14YC or Kohler 6613201-S |
Spark plug gap: | 0.76 mm (0.030 in) |
Spark plug torque: | 27 N·m (2.8 kg·m, 19.9 ft·lb) |
Ignition module air gap: | 0.20-0.30 mm (0.008-0.012 in) |
Cooling system | |
Cooling system: | Liquid-cooled cooling system with parallel-flow radiator and integrated belt-driven water pump |
Coolant capacity: | 2.0 liters (2.1 US.qts, 1.8 Imp. qts) |
References
1. Kohler Aegis LH630, LH640, LH685, LH690, LH750, LH755 service manual. Kohler Co. 2021.
We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.
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